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January 15, 2009

Sun-Reflecting Crops Could Cool Global Temperatures

by Sam Savage

Researchers in Britain reported Thursday that sun-reflecting crops could help lower temperatures and limit global warming. The strategy of having farmers grow these crop varieties, which reflect more sunlight into the atmosphere, could cool much of North America, Europe and parts of North Asia by as much as one degree Celsius during the summer growing season.

It would also reduce by 20 percent a predicted 5 degrees Celsius temperature rise for the region by the end of the century, said Andy Ridgwell, who led the study.

"We found that different varieties of most food crops do differ in how much solar energy is reflected back to space," Ridgwell told Reuters.

"The more energy you reflect back to space the cooler the air temperatures will be."

Scientists and governments the world over are looking for new ways to slow the global warming that experts believe will cause droughts, heat waves, rising sea levels, more powerful storms and the extinction of some species.

Prior studies have shown that maize, wheat, barley and sorghum reflect solar energy according to how waxy or hairy a plant's surface is or how its leaves are arranged. And since its likely that these qualities also hold true of all food crops, the current research points to a potential low-cost strategy with high payoffs in terms of fighting rising temperatures, Ridgwell said.

The plan differs greatly from biofuels because food production, either in terms of yield or type, would not need to be disrupted, said Ridgwell.

"The idea is you could continue to grow maize, for example, but you could grow a variety that has a bigger climate benefit," he said.

"You are not replacing food crops with something you turn into energy."

The effect would be most pronounced in North America, Europe and Northern Asia, where most of the Earth's croplands are located, he noted.

The reduction would be equivalent to a yearly global cooling of more than 0.1 degree Celsius, or roughly 20 percent of the 0.6 rise since the time of the Industrial Revolution.

The research also raises the possibility that farmers could receive carbon credits to promote the growing of such sun-reflecting varieties, and ensure they remain robust, Ridgwell said.

"You could use selective breeding for climate characteristics," he said. "This seems very doable without spending lots of money."